The present invention relates to sound reproducing equipment such as loudspeakers and the like which are light in weight, economical to produce, and which possess improved acoustical characteristics. More particularly, the invention is directed to sound reproducing equipment in which the acoustic diaphragm is compliantly mounted with respect to a housing for relatively free longitudinal movement, while being maintained in a predetermined lateral position.
Various suspension systems have been designed in an attempt to increase the power handling capabilities of loud speakers without correspondingly increasing the distortion introduced due to the suspension system. In this regard, it is desired for maximizing acoustic power radiated to provide for increased diaphragm excursions for a given frontal area of the diaphragm. Examples of such prior art systems are disclosed in U.S. Pat. No. 2,439,666 to Marquis, U.S. Pat. No. 2,490,466 to Olson et al, and U.S. Pat. No. 3,019,849 to King.
In these prior art systems, the loudspeakers employ cone shaped diaphragms which are compliantly supported within the loudspeaker frame or housing. The diaphragm carries a voice coil and voice coil form which is arranged within an air gap provided by a permanent magnet assembly which serves as a driving force for causing excursion of the diaphragm. In these prior art arrangements, compliant supporting members support both the enlarged peripheral portion of the cone shaped diaphragm as well as the small end of the diaphragm which carries the voice coil form and voice coil. In other words, both the outer peripheral edge of the diaphragm as well as the centrally located portion are supported relative to the frame by compliant members which serve to center the diaphragm (for proper orientation of the voice coil within the air gap provided in the magnetic assembly) and to allow free longitudinal or axial movement of the diaphragm. For example, in both the Marquis and Olson et al references, these compliant supports are provided by a pair of corrugated compliant ring members which are corrugated transverse relative to the direction of longitudinal movement. That is, the compliant coupling members are each a laterally extending ring having a plurality of ridges or corrugations extending out of the plane thereof. Such compliant members are designed to limit radial or lateral motion of the diaphragm while permitting movement in the longitudinal direction as a result of bending of the ring members. In the King patent, the compliant member at the small end of the frustro-conical diaphragm (commonly known as a spider) is of the conventional laterally extending ring type which may comprise a spring or laterally extending ring elements having ridges extending out of the plane thereof, as in the Marquis or Olson et al references. On the other hand, the compliant member at the peripheral base portion in the King patent comprises a circular bellows type corrugated compliant member which is corrugated in the longitudinal direction so as to permit longitudinal movement in the manner of an accordian.
One problem of the prior art has been the necessity of compliant members which extend and are attached laterally to the speaker housing to provide for the necessary lateral stability of the support system to maintain the proper alignment of the voice coil relative to the magnet driving assembly. In the Marquis and Olson et al references, such laterally extending compliant members were attached at both the peripheral base portion and the small end of the cone shaped diaphragm, whereas in the King reference such a compliant member was only provided at the small end of the cone shaped diaphragm. Such arrangements limit the frequency response capable of being achieved for a given speaker size, as well as introducing distortion into the system as a result of edge type reflection due to the radial or lateral connection of the compliant members to the loudspeaker housing.
Another problem of the prior art arrangements has been that the compliant support for supporting the diaphragm encroaches upon the area of the diaphragm, thus limiting the effective area of the radiating surface for a given housing size. This is readily apparent from the structures shown in the Olson et al and Marquis patents, in which the radially extending rings circumferentially surround the peripheral edges of the diaphragm and are located between the frame and the edge of the diaphragm. The King patent attempts to overcome this problem by utilizing an axially extending corrugated compliant member for the outer peripheral portion of the diaphragm. However, it is to be noted that the outer peripheral edge of the diaphragm is attached to or between a pair of corrugations. Thus, while this structure does reduce the amount of encroachment on the effective radiating area, it still encroaches on that area.
These and other disadvantages of the prior art are overcome with the present invention.